<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="vue221.js"></script>
    <!--<script src="vue-router231.js"></script>-->
</head>
<body>
<div id="app">
    <input type="text" v-model="firstName">+
    <input type="text" v-model="lastName">=
    {{fullName}}
</div>
</body>
<script>
    new Vue({
        el:'#app',
        data:{
            firstName:'',
            lastName:'',
        },
        computed:{
            fullName:function(){
                return Number(this.firstName)+Number((this.lastName))
            }
        }
    })
</script>
</html>